The present invention generally relates to node apparatuses, and more particularly to a node apparatus of a communication network employing a multi-conjunction architecture.
A multi-channel lattice communication network applicable to local area networks (LANs), public line networks and especially to a multi-media communication was previously proposed in a U.S. patent application Ser. No. 096,532 filed Sept. 15, 1987 in which the assignee is the same as the assignee of the present application. The proposed lattice communication network is analogous to nerve cells of a living body, and employs node apparatuses. Each node apparatus has a plurality of input and output channels and is used as a communication controleelement. Such node apparatuses are coupled in a multi-conjunction to constitute the lattice communication network. Each node apparatus transfers one of incoming digital signals according to a first-come-first-served logic (hereinafter simply referred to as a first-come-first-output logic).
The proposed lattice communication network has a large degree of freedom of network topology because of the multi-conjunction architecture. Thus, the survivability of data is high. In other words, even when a fault occurs in a path of the communication network, it is possible to carry out the communication through other paths. Furthermore, it is possible to select optimum paths for the communication because each node apparatus transfers the incoming digital signals according to the first-come-first-output logic.
On the other hand, the proposed lattice communication network employs a multi-channel system in which a plurality of connecting channels are established, so as to effectively achieve a full duplex communication. The proposed lattice communication network is effectively applicable to the physical layer to the network layer of the open system interconnection (OSI), for example.
When making a communication in the proposed lattice communication network, a node apparatus which receives a signal broadcasts the signal to other node apparatuses or terminal devices and waits for an acknowledge signal or returning signal sent back from a destination terminal device. A communication path is fixed when the acknowledge signal is received from the destination terminal device, and the node apparatus which receives the acknowledge signal enters an end sequence. The node apparatus is initialized and is ready to receive and broadcast a new signal after the end sequence is ended.
When a new communication path is fixed in the proposed lattice communication network, a node apparatus in the fixed communication path immediately enters the end sequence. However, other node apparatuses not included in the fixed communication path continue to carry out a time-out operation for detecting an end of the signal, that is, an end of the communication, and enter the end sequence only after the time-out operation is ended. In other words, a node apparatus not included in the fixed communication path confirms that no signal is received for a predetermined time before entering the end sequence.
In the proposed lattice communication network, the predetermined time is set longer than a time it takes for the node apparatus in the fixed communication path to be initialized so as to get ready to receive and broadcast a new signal. In other words, even when the node apparatus in the fixed communication path is already initialized through the end sequence and is ready for the new communication, the node apparatus not included in the fixed communication path is not yet initialized and it takes a certain time before the node apparatus not included in the fixed communication path is finally initialized.
As a result, when the new communication is started in a state where the node apparatus in the fixed oommunication path is already initialized but the node apparatus not included in the fixed communication path is not yet initialized, the node apparatus not included in the fixed communication path cannot carry out a normal reception and broadcasting of the new signal because it is not yet initialized. Such a problem will not occur if the new communication were to start after it is certain that the node apparatus not included in the fixed communication path is initialized, however, a terminal device which starts the new communication has no means of detecting whether or not a node apparatus in the lattice communication network is initialized.